Steam reforming

• US 4,750,986 A
• Filed: 08/19/1985
• Issued: 06/14/1988
• Est. Priority Date: 03/25/1983
• Status: Expired due to Term

• Current Assignee: Johnson Matthey PLC
• Original Assignee: Imperial Chemical Industries PLC (IMPERIAL CHEMICAL INDUSTRIES)
• Inventors: Pinto, Alwyn
• Primary Examiner(s): Richman, Barry S.
• Assistant Examiner(s): Johnson, W. R.
• Application Number:
  US06/767,067
• Time in Patent Office: 1,030 Days
• Field of Search: 422/148, 422/193, 422/197, 422/312, 423/360-362, 518/706, 518/715, 252/373, 366/336-339, 165/109 T, 165/184, 208/64, 208/68, 208/79, 208/134
• US Class Current: 208/64
• CPC Class Codes: B01J 12/005 carried out at high temperatures, e.g. by pyrolysis
• CPC Class Codes: B01J 19/2425 in parallel
• CPC Class Codes: B01J 2208/00185 Fingers
• CPC Class Codes: B01J 2208/00212 Plates; Jackets; Cylinders
• CPC Class Codes: B01J 2208/00849 outside the bed, e.g. baffles
• CPC Class Codes: B01J 2219/00078 Fingers
• CPC Class Codes: B01J 2219/00085 Plates; Jackets; Cylinders
• CPC Class Codes: B01J 2219/00094 Jackets
• CPC Class Codes: B01J 8/062 being installed in a furnace
• CPC Class Codes: C01B 3/025 Preparation or purification of gas mixtures for ammonia synthesis

Abstract

The endothermic reaction of a hydrocarbon feedstock with steam and/or carbon dioxide is carried out using a double-tube reactor. In one preferred form of the reactor the catalyst is present as a coating on the outside of the inner tube. In another form inner tubes are mounted in one tube-plate and the other tubes in a second tube plate and the tube plates are disposed across a cylindrical shell so as to define a heat exchange zone (provided with a heat source) a reactants feed zone and a products offtake zone. The heat source is preferably a burner, to be fed with the product of the endothermic reaction, followed by a secondary reforming catalyst. The apparatus makes possible processes for making raw hydrogen-containing gases with advantageous internal heat recovery.

Claims

1. A process for the production of a hydrogen and nitrogen containing gas stream suitable for use in the production of ammonia synthesis gas comprising;

(i) reacting a mixture of a hydrocarbon feedstock and steam in a first zone containing a steam reforming catalyst to produce a primary reformed gas stream containing hydrogen, carbon oxides, methane and unreacted steam,

(ii) partially combusting said primary reformed gas stream with a member of the group consisting of air, and oxygen enriched air, so as to provide a hot, partially combusted, gas stream,

(iii) reacting said hot, partially combusted, gas stream in a second zone containing a secondary steam reforming catalyst so as to decrease the methane content of said gas stream to form a product gas stream, and

(iv) simultaneously transferring heat from said primary reformed gas stream leaving said first zone and from said product gas stream leaving said second zone to said mixture while said mixture is in said first zone, so as to supply the heat required for the endothermic reaction in said first zone, and to provide a cooled primary reformed gas stream and a cooled product stream.

2. A process according to claim 1 carried out at a pressure in the range 10-60 bar abs.

3. A process according to claim 1 wherein the product gas is subjected to the shift reaction followed by removal of carbon oxides, the proportion of air or oxygen enriched air employed in said partial combustion step being such that, after said removal of carbon oxides, the gas stream has a H₂ :

N₂ ratio below 2.5.

4. A process according to claim 1 wherein the cooled primary reformed gas stream is further cooled, before the partial combustion step, by heat exchange with the mixture of hydrocarbon feedstock and steam to effect preheating of said mixture before it enters said first zone.

5. A process according to claim 4 wherein

(I) said first zone comprises a plurality of annular zones extending into a heat exchange zone from a plenum zone, each annular zone

(a) is closed at a first end remote from the plenum zone and opens at a second end into the plenum zone,

(b) contains the steam reforming catalyst, and

(c) surrounds a tube that is open at the first end of the associated annular zone, and which extends the length of the annular zone and through the plenum zone,

said heat exchange zone being downstream of the second zone so that the product gas leaving the second zone passes through the heat exchange zone, whereby each annular zone

is heated from the outside by the product gas steam passing through the heat exchange zone, and

is heated from the inside by the primary reformed gas stream leaving that annular zone through the tube associated therewith, and

(II) the mixture of hydrocarbon and steam is fed to the plenum zone wherein, prior to said mixture entering said annular zones, it is heated by the primary reformed gas stream flowing through the tubes extending through said plenum zone.

6. A process for the production of a hydrogen and nitrogen containing gas stream suitable for use in the production of ammonia synthesis gas comprising

(i) passing a mixture of a hydrocarbon feedstock and steam through a first zone containing a steam reforming catalyst to produce a primary formed gas stream containing hydrogen, carbon oxides, methane and unreacted steam,

(ii) cooling said primary reformed gas stream by heat exchange with said hydrocarbon feedstock and steam mixture while said mixture is in said first zone so as to supply part of the heat required for the reaction in said first zone and to provide a partially cooled primary reformed gas stream,

(iii) further cooling said partially cooled primary reformed gas stream by heat exchange with said hydrocarbon feedstock/steam mixture before it enters said first zone so as to effect preheating thereof and to produce a cooler primary reformed gas stream,

(iv) partially combusting said cooler primary reformed gas stream with a member of the group consisting of air, and oxygen enriched air, so as to provide a hot, partially combusted, gas stream,

(v) passing said hot, partially combusted, gas stream through a second zone containing a secondary steam reforming catalyst so as to decrease the methane content of said gas stream to form a product gas stream, and

(vi) cooling said product gas stream by heat exchange with said mixture of hydrocarbon feedstock and steam after the preheating of said mixture and while said mixture is in said first zone so as to supply the remainder of the heat required for the reaction in said first zone and to provide a cooled product gas stream.

7. In a process for the production of a hydrogen and nitrogen containing gas stream suitable for use in the production of ammonia synthesis gas comprising:

(i) reacting a mixture of a hydrocarbon feedstock and steam in a first zone containing a steam reforming catalyst to produce a primary reformed gas stream containing hydrogen, carbon oxides, methane and unreacted steam,

(ii) partially combusting said primary reformed gas stream with a member of the group consisting of air, and oxygen enriched air, so as to provide a hot, partially combusted, gas stream,

(iii) reacting said hot, partially combusted, gas stream in a second zone containing a secondary steam reforming catalyst so as to decrease the methane content of said gas stream to form a product gas stream, and

(iv) providing heat for the endothermic reaction in said first zone by transferring heat from said product gas to said hydrocarbon feedstock and steam mixture while said mixture is in said first zone, the improvement comprising transferring heat from said primary reformed gas stream leaving said first zone to said mixture while said mixture is in said first zone simultaneously with the transfer of heat from the product gas stream to said mixture.